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Clinical Paper Oral Surgery Factors influencing the prophylactic removal of asymptomatic impacted lower third molars N. Almendros-Marque´s, E. Alaejos-Algarra, M. Quinteros-Borgarello, L. Berini- Ayte´s, C. Gay-Escoda: Factors influencing the prophylactic removal of asymptomatic impacted lower third molars. Int. J. Oral Maxillofac. Surg. 2008; 37: 29–35. #2007 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. N. A
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  Clinical PaperOral Surgery Factors influencing theprophylactic removal ofasymptomatic impacted lowerthird molars  N. Almendros-Marque´  s, E. Alaejos-Algarra, M. Quinteros-Borgarello, L. Berini- Ayte´  s, C. Gay-Escoda: Factors influencing the prophylactic removal of asymptomaticimpacted lower third molars. Int. J. Oral Maxillofac. Surg. 2008; 37: 29–35. # 2007International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. N. Almendros-Marque´ s,E. Alaejos-Algarra,M. Quinteros-Borgarello,L. Berini-Ayte´ s, C. Gay-Escoda Master Program of Oral Surgery andImplantology, Barcelona University DentalSchool, Barcelona, Spain  Abstract.  Theaimofthisstudywastoanalysefactorsindicatingprophylacticremovalof impacted lower third molars, and how they, and possibly surgeon experience,influence the therapeutic decision-making process. A descriptive observationalstudy was made of 40 asymptomatic impacted lower third molars.Orthopantomographs were scanned and presented to four professionals withdifferent degrees of surgical experience. The examiners received informationrelating to patient age and sex, molar inclination and degree of impaction, and expressed their opinion on the necessity for teeth removal. There was a statisticallysignificant relationship between examiner decision and the estimated probability of  pathology if the molars were not removed ( P < 0.05). The degree of influence onthe decision to extract was in decreasing order: estimated risk of complications,inclination of molar, age, degree of impaction and patient sex. No statisticallysignificant differences ( P > 0.05) were observed between residents and trainers interms of the decision to remove or estimated risk of complications. Themanagement approach adopted by oral surgeons regarding the removal of asymptomatic impacted lower third molars depends upon the perceived risk of complications if such teeth are not removed, other factors being secondary. Thesurgical experience of the professional does not seem to influence treatmentdecision. Key words: third molar; prophylactic removal;therapeutic decision.Accepted for publication 15 June 2007Available online 30 October 2007 Theremovalofimpactedmolarsisthemostcommon operation in oral surgery. Reportsindicate that 18–40% of all extracted molars are asymptomatic 16,23 , and consid-erablecontroversyexistsregardingthebestmanagementoptionforsuchcases 41 .AttheConsensus Conference 34 held in 1979(National Institutes of Health), guidelineswere established for the removal of patho-logical molars, although no clear agree-ment was reached on the prophylacticremoval of those teeth that remain asymp-tomatic.Thislackofconsensusgaverisetotwo distinct tendencies, some surgeonsfavouring a conservative approach, whileothers opted for more interventional stra-tegies. Those in favour of prophylacticremoval argued that extraction reduces  Int. J. Oral Maxillofac. Surg. 2008; 37: 29–35 doi:10.1016/j.ijom.2007.06.008, available online at http://www.sciencedirect.com 0901-5027/01029+07 $30.00/0  # 2007 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.  the incidence of complications secondaryto impaction, and also reduces the morbid-ity associated with extraction when per-formed in elderly patients 21,28,37 . Incontrast, those in favour of a more conser-vativeapproach consideredit betterto waitfor pathological changes to appear beforeindicating extraction 39 .M ERCIER   & P RECIOUS 29 considered thatlack of knowledge of the natural course of impacted teeth precludes the definition of indications for preventive molar removal,since the risks and benefits of the differenttreatment approaches are not clear. K  OS-TOPOULOU  et al. 19 , after evaluating thetherapeutic decisions of 28 professionals(10 oral surgeons and 18 general dentists)in a series of 36 asymptomatic molars,concluded that extensive variability incriteria exists among members of thesamediscipline.In view of the limited availability of longitudinal studies providing specificinsight into the pathological evolution of tooth impaction, treatment decision has become an intuitive and somewhat arbi-trary process subject to the individualcriterion of each professional. Such cri-teria in turn are based on three fundamen-tal aspects: patient information, thecharacteristics of dental impaction, and information based on the existing clinicaland scientific evidence.The present study analyzed the factorsdetermining the indication for prophylac-tic removal of impacted lower third molars, and the degree to which suchfactors influence the decision-making pro-cess. The possible influence of surgeonexperience upon the decision to extractsuch teeth was also examined. Materials and methods Data sampling A descriptive observational study wasmade of 40 asymptomatic impacted lower third molars in patients consecutivelyseen for lower third molar removal. Thecorresponding orthopantomographs werescanned (resolution 350 dpi) and pre-sented to four professionals with differentdegrees of surgical experience (two trai-ners and two residents of the Master of OralSurgeryandImplantology,BarcelonaUniversity Dental School, Spain). Each professional received information relatingto patient age and sex, molar inclinationand degree of impaction, and the absenceof symptomatology (Fig. 1).For each molar, the examiners com- pleted a questionnaire addressing the deci-sion to perform removal, the degree of confidence in the indication for prophy-lactic removal, and the estimated risk of development of general and specific pathology (cysts, pericoronitis, periodon-tal lesions, distal surface caries of thesecond molar, root resorption of the sec-ond molar) if extraction was not per-formed. Such assessment was based onthe use of 100-mm visual analog scales. Third molar classification The third molars were categorized accord-ing to the classifications of P ELL  & G RE-GORY 31 and W INTER  46 , using RadioMemory software (Copyright 1 2003,Radio Memory Ltd., Version 1-Release5, Belo Horizonte, Brazil), and by tracingthe following four lines on the scanned orthopantomographs.- Line of the occlusal plane, established  by the occlusal surfaces of the first and second lower molars.- Cervical line,established bythecervical bone margin of the second lower molar.These first two lines allow classificationof the molars on the basis of their depth(Pell and Gregory positions A, B and C).- Line of the anterior margin of theascending ramus of the mandible, indi-cating the position of the molar withrespect to the ascending ramus (Pelland Gregory classes I, II and III).- Line of the longitudinal axis of themolar, which forms an angle with theocclusal plane delimiting the inverted,horizontal, mesioangular, vertical or distoangular inclination of the tooth(Winter classification).Determination of the angle between theocclusalplaneoralineparalleltothelatter and the longitudinal axis of the molar allowed objective classification of thethird molars within the correspondingWinter subclasses. Accordingly:- molars with a negative angle ( < 0 8 ) wereconsidered to be inverted,- molarswithananglebetween0 8 and30 8 were considered to be horizontal,- molars with an angle between 31 8  and 60 8 wereconsideredtobemesioangular,- molars with an angle between 61 8  and 90 8  were considered to be vertical,- molars with an angle  > 90 8  were con-sidered to be distoangular.The data relating to patient age and sex,and to the type of mucosal coverage of themolars, were obtained directly from thecase histories. The teeth were divided intomolars without mucosal coverage, molarswith partial mucosal coverage, and molarswith total mucosal coverage. The teethwerelikewisedividedintotwoagegroups, belonging to patients aged    30 and   > 30years of age. Statistical analysis The data obtained were analyzed using theSPSS version 12.0 statistical package(SPSS Inc., Chicago, IL, USA) for Micro-soft Windows (Barcelona Universitylicense), with application of the followingstatistical tests.- Analysis of the statistical association between tooth removal decision and theappearance of complications secondary 30  Almendros-Marque´  s et al.  Fig. 1 . Case presented to the examiners for assessment of the removal of asymptomatic molar 4.8.  to impaction, based on the CATREG procedure, which performs categoricalregression through optimum scaling.- Analysis of the impact of the variablesupon removal decision using the generallinear model (GLM) and CATREG pro-cedure.- Analysis of the differences betweenresidents and trainers based on unifac-torial analysis of variance (ANOVA,means equality robustness tests and var-iance homogeneity testing). Results The examiners indicated prophylacticremovalof95%of themolarsintheseries,with a mean confidence of 87%. The mean probability of expected future complica-tionswas84%.Inturn,theestimatedmean probability of developing specific clinicalmanifestations was 47% for cystic com- plications, 71% for pericoronitis, 61% for  periodontal lesions of the distal surface of thesecondmolar, and26%forrootresorp-tion of the second molar. Table 1 showsthe distribution of the impacted molars bysex, age, degree of impaction, inclination,mucosal and bony coverage.A statistically significant relationshipwas observed between examiner decisionto remove the impacted teeth, the confi-dence with which the indication for removalwasestablished,and theestimated  probability of cyst pathology and rootresorption in the event that the asympto-matic molars were not removed (  P < 0.05)(Table 2). The  P -value of combined sig-nificance contrasting with the ANOVA F-testwaslow(  P  = 0.05),showingtheglobalsignificance of the model to be high(Table 3).The degree of influence of the studyvariables upon the decision to extract anasymptomatic molar was as follows, indecreasing order: estimated risk of com- plications, inclination of the molar, patientage, degree of impaction according to Pelland Gregory classification, and patient sex( b  parameter) (Table 4). Of these vari-ables, only the estimated probability of complications showed a statistically sig-nificant association with the therapeuticdecision of the examiners (  P < 0.05).There were no statistically significantdifferences interms of tooth removaldeci-sion or the perceived probability of com- plications in the form of cysts, periodontallesions of the distal surface or root resorp-tionof thesecond molar between residentsand trainers (  P > 0.05) (Tables 5–7). Themean length of surgical experience of theexaminers was 6 years (1.5 years for resi-dents and 10.5 for trainers). Discussion The correct diagnosis of dental impactionrequires a detailed anamnesis and clinicalexamination, and the use of complemen-tary tests to allow correct treatment deci-sions to be taken. Two managementoptions can be considered in the case of asymptomatic impacted third molars: pro- phylactic removal, with the aim of avoid-ing the morbidity associated with toothextraction in elderly patients, and conser-vative management in which the teeth arenot removed until they develop patholo-gical manifestations. According to the lat-ter approach, patients should be subjected to periodic clinical and radiological eva-luation in order to detect such alterationsas quickly as possible.To date, the therapeutic decision for  planning the treatment of asymptomaticimpacted third molars has been based onthe existing body of clinical and scientificevidence. Regarding the position of such  Prophylactic removal of asymptomatic impacted lower third molars  31 Table 1 . Distribution of molars by sex, age, position, inclination, mucosal and bony coverageVariable Category No. of cases (%)Sex Male 19 47.5Female 21 52.5Age Up to 30 years 28 70Over 30 years 12 30Position IIA 13 32.5IIIA 1 2.5IIB 24 60IIIB 2 5Inclination Mesioangular 15 37.5Distoangular 6 15Vertical 14 35Horizontal 5 12.5Mucosal coverage Without 1 2.5Partial 12 30Total 27 67.5Bony coverage Without 1 2.5Partial 28 70Total 11 27.5 Table 2 . Analysis of statistical association between decision to remove and different variablesTypified coefficientsVariable Beta Standard error Degrees of freedom  F   parameter SignificanceConfidence   0.363 0.072 1 25.312 0.000Cyst   0.465 0.068 1 46.944 0.000Pericoronitis   0.058 0.070 1 0.684 0.410Periodontitis   0.165 0.098 2 2.810 0.064Caries   0.069 0.090 1 0.596 0.442Root resorption 0.189 0.081 2 5.453 0.005 Table 3 . Analysis of variance relating to global significance of the modelSum of squaresDegree of freedomQuadraticmean  F   parameter SignificanceRegression 73,867 8 9.233 19.194 0.000Residual 60,133 125 0.481Total 134,000 133 Table 4 . Influence of variables upon decision on tooth removalTypified coefficientsVariable Beta Standard error Degrees of freedom  F   parameter SignificanceAge   0.075 0.056 2 1.800 0.169Sex   0.014 0.056 2 0.062 0.940Complication   0.768 0.053 4 208.168 0.000Position 0.069 0.054 2 1.632 0.199Inclination 0.085 0.054 2 2.461 0.089  molars, partial mucosal coverage has beenshown to favour the appearance of  infec-tious complications (pericoronitis) 2,22,27 ,while mesioangular and horizontal posi-tionsareassociatedwithcaries,rootresorp-tion and periodontal disorder s of the distalsurface of the second molar  10,27,40 . Totalmucosal and bony coverage constitutes aneffective barrier against bacterial invasion, partial mucosal retention implying a 22– 34-fold greater risk of complications 16 . Asregards the age at which the patient issubjected to surgery, it is known that per-iodontalhealingofthesecondmolarandof the surgical wound is more favourable inindividuals under the age of 25–30years 20,24,36,42 . Patient age has been identi-fied as a prognostic factor in the course of lesions affecting the inferior alveolar nerve 33,43 ,andthemorbidityofthesurgicaloperationincreasesinproportiontotheageof the patient 7,35 .The risk of damage to the inferior alveo-lar or lingual nerves during operation has beenareasonforreducingthefrequencyof extraction of impacted third molars.Although usually temporary, paraesthesia(probably as a result of neuropraxia) or anaesthesia (probably caused by axonotm-esis) may persist for a variable period dependingonthetypeofinjury.Permanentnumbness is fortunately uncommon. Theincidenceofnervedamageafterthirdmolar surgery is frequently reported, rangingwidelyfrom0.2to23% 1,13,45 .Somestudieshave shown that the inferior alveolar nervemay be temporarily damaged in 1.3–7.8%of cases, with permanent damage in lessthan 1% 8,11,38 . The lingual nerve may betemporarily injured in 2.1–15% of casesandpermanentlyinjuredinupto1% 6,8,25,38 .Theprofessionalsinthisstudyindicated removal of 95% of all molars in the sam- ple, with a mean confidence of 87.36%.This agrees with the high estimated mean probability that such third molars would develop some form of pathology if notremoved (83.5%). This may be because70% of the affected teeth belonged to patients under 30 years of age, and mostof the third molars in the series were in positions IIA (32.5%) and IIB (60%) of the classification of Pell and Gregory,these being the positions most often asso-ciated  with the development of pericoro-nitis. 2 Pericoronitis is the most common pathosis associated with mandibular third molars with a varia bly reported incidence.P UNWUTIKORN  et al. 32 found an incidenceof pericoronitis near to 24%, a low rate incomparison with those reported by others( > 54%) 4,16,37 .The perceived risk of specific complica-tions also seems to be related to the char-acteristics of the study sample. Thus, the perceived risk of caries and periodontaldamage of the distal surface of the second molar,commonlyassociatedwithmesioan-gular and horizontal impaction 10,27,40 , wasrespectively estimated to be 48.42 and 60.76%. These percentages coincide withtheincidenceofmesioangularandhorizon-tal impaction in this series (50%). Theincidence of caries of the distal surface of thesecondmolar reportedbymanyauthorsisnearto7–8% 3,4 ,whilethatofperiodontallesions of the distal surface of the second molar is estimated as 10% 4 .The root resorption of the second molar is also associated to horizontal or mesioangular third molars with total bonycoverage 30 . Twenty-five percent of themolars in this series presented in these positions (three horizontal total intrabonymolars and seven mesioangular teeth), inagreement with the estimated mean risk of root resorption (25.56%), an overesti-mated rate in comparison with thatreported in the literature ( < 1%) 3,4 .For the professionals participating in thestudy, the fundamental factor influencingthe decision to extract an impacted molar was the perceived risk of the developmentof clinical manifestations (  P < 0.05). Inaddition, the inclination of the tooth(  P  = 0.089) and the age of the patient(  P  = 0.016) were important factors in thedecision-making process, despite the factthat they showed nostatistically significantassociation to the treatment decisionadopted. These observations are compar-able to those published in 2001 by K   NUTS-SON  et al. 17 , where patient sex and agelikewise showed no statistically significantcorrelation to the decision on prophylacticremoval. The professionals were moreinclined to remove distoangular molars presenting partial mucosal coverage in patients between 19 and 25 years of age,andalsohorizontalteethwithpartialortotalmucosal coverage in patients between 19and 40 years of age. In 1999, L IEDHOLM et al. 23 found patient age to exhibit astatistically significant correlation to thedecision on prophylactic removal of asymptomatic molars, unlike other factorssuch as the inclination and type of im pac-tioninvolved.AccordingtoK  OERNER  18 ,thedecision to remove asymptomatic teethshouldbeconditionedbytheperceivedrisk of clinical manifestations derived fromimpaction, the age of the patient and the position of the molar. In another study,K   NUTSSON  et al. 15 examined three factorsthat influence the decision of prophylacticremoval: the age of the patient, dentalinclination, and type of third molar impac-tion involved. They concluded that the 32  Almendros-Marque´  s et al. Table 5 . Analysis of variance of differences between residents and trainers in relation to thedifferent study variablesSum of squaresDegrees of freedomQuadraticmean  F   parameter SignificanceDecisionInter-group 0.000 1 0.000 0.000 1.000 * Intra-group 9.375 158 0.059ConfidenceInter-group 5040.025 1 5040.025 15.886 0.000Intra-group 50126.950 158 317.259ComplicationInter-group 6838.225 1 6838.225 17.502 0.000Intra-group 61731.775 158 390.707CystInter-group 644.006 1 644.006 0.747 0.389 * Intra-group 136226.087 158 8620.190PeriodontitisInter-group 400.056 1 400.056 0.363 0.548 * Intra-group 174205.438 158 1102.566CariesInter-group 19602.756 1 19602.756 19.829 0.000Intra-group 156198.188 158 988.596Root resorptionInter-group 3053.756 1 3053.756 2.971 0.087 * Intra-group 162407.738 158 1027.897PericoronitisInter-group 12531.600 1 12531.600 17.073 0.000Intra-group 115970.000 158 733.987 *  P > 0.05 indicates equality of means.
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